1. Field of the Invention
The present invention relates to image projectors. More specifically, the present invention relates to methods and apparatus for dynamic distortion correction in image projectors.
While the invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
An aircraft simulator is utilized to train pilots to successfully perform air maneuvers. The simulator is designed to emulate actual flight conditions and can be constructed to, for example, position the pilot in a cockpit which is located approximately at the center of a large dome. The dome is typically forty feet in diameter and can include two image projectors. Each projector is designed to project a display image onto the surface of a large dome screen. The first image projector is located outside and at the rear of the dome while the second image projector is located outside but at the front of the dome.
The two projectors are positioned to project television raster images on the forward and rearward hemispherical surfaces, respectively, of the dome. The light from each projector enters through a small hole in the side of the dome which is typically 3/8" or less in diameter. An optical system creates high resolution displays yet the pilot sees minimal light emanating through the hole. Each image projector includes a gimballed mirror which is employed to steer the display image anywhere within the respective hemisphere opposite to the image projector. In general, the display image is constantly moving across the dome surface.
However, a problem exists in that the display image, as seen by the pilot positioned at the center of the dome, becomes increasingly distorted as the viewing angle increases. The viewing angle (V) is defined as that angle between the axis of the image projector through the center of the dome and the line from the center of the dome to the center of the display image on the dome surface screen. These known distortions are caused by the projecton of television images onto a curved screen (e.g., the dome surface screen) from an extreme off-axis projection point. Therefore, in order for a pilot located at the center of the dome to see an undistorted display image regardless of the location of the display image on the dome screen, it is necessary to correct the distortion problem. This type of distortion correction is referred to as dynamic distortion correction.
In the past, dynamic distortion correction was performed in a computer image generator. In general, the computer image generator functioned to provide the source of the display image projected onto the dome surface screen. It is noted that only certain computer image generators, such as the General Electric Compuscene IV, are equipped to perform dynamic distortion correction. Unfortunately, the dynamic distortion correction option, when combined with the other features of the computer image generator, is prohibitively expensive and, therefore, is not a viable option.
Thus, there is a need in the art for an improvement in dynamic distortion correction of the display image at a large viewing angle which is economical and which will permit use of a computer image generator which does not offer the dynamic distortion correction option.